STOP HAVING AIR PUMPED INTO THE SYSTEM. Pumping air into the system ruins the drier. Did you know that it is recommended to replace the drier each time the system is opened? That's because the drier gets exposed to the atmosphere and the dessicant quickly becomes saturated with moisture. Pumping air into the system is much much worse than just briefly opening it up to atmospheric humidity.

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08 W251 R350
97 W210 E320
91 W124 300E
86 W126 560SEL
85 W126 380SE Silver
85 W126 380SE Cranberry
79 W123 250
78 W123 280E
75 W114 280